Phytochemical Screening and In vitro Antimicrobial Evaluation of Rhizome Extracts of Cochlospermum tinctorium perr. ex A. Rich

Abstract

This study evaluated the qualitative phytochemical profile and in vitro antimicrobial activity of rhizome extracts of Cochlospermum tinctorium Perr. ex A. Rich. The rhizomes were collected from Bauchi State, Nigeria, authenticated, cleaned, dried, pulverised and extracted successively by cold maceration using solvents of increasing polarity: n-hexane, toluene, diethyl ether and distilled water. Extract recovery from 250 g of powdered rhizome was 3.34 g (1.34%) for n-hexane, 7.63 g (4.08%) for toluene, 3.46 g (1.90%) for diethyl ether and 12.05 g (7.01%) for distilled water. Qualitative phytochemical screening was conducted for alkaloids, flavonoids, tannins, saponins, phenols, glycosides and anthraquinones. Antimicrobial activity was assessed using the agar well diffusion method against Escherichia coli, Salmonella typhi, Staphylococcus aureus, Streptococcus pneumoniae, Candida albicans and Aspergillus niger. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth dilution and subculture methods, respectively. The extracts produced inhibition zones that ranged from 0.00 to 21.50 mm across the tested organisms and concentrations. The toluene extract showed the highest recorded activity, with a 21.50 mm inhibition zone against E. coli at 400 mg/mL, followed by the distilled water extract, which produced an 18.00 mm zone against the same organism at 400 mg/mL. Activity generally increased with concentration. MIC values ranged from 50 to 400 mg/mL, while recorded MBC values ranged from 100 to 400 mg/mL for susceptible organisms. No extract showed an MBC against A. niger. These findings indicate that C. tinctorium rhizome extracts contain phytochemical constituents and exhibit measurable in vitro antimicrobial activity under the conditions of this study.